Numerous processes are within the purview of those skilled in the art for preparing toner. Emulsion aggregation (EA) is one such method. Emulsion aggregation techniques may involve a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in entirety. Other examples of emulsion/aggregation/coalescing processes for the preparation of toners are illustrated in U.S. Pat. Nos. 5,902,710; 5,910,387; 5,916,725; 5,919,595; 5,925,488, 5,977,210 and 5,994,020, and U.S. Pub. No. 2008/0107989, the disclosure of each of which hereby is incorporated by reference in entirety.
Polyester toners can utilize amorphous and crystalline polyester resins as illustrated, for example, in U.S. Pub. No. 2008/0153027, the disclosure of which is hereby incorporated by reference in entirety. The incorporation of the polyesters into toner requires formulation into emulsions prepared by, for example, batch processes containing solvent, for example, solvent flash emulsification which is a time and energy-consuming process.
Solvent-less latex emulsions have been formed in either a batch or extrusion process through the addition of a neutralizing solution, a surfactant solution and water to a thermally softened resin as illustrated, for example, in U.S. Pub. Nos. 2009/0208864 and 2009/0246680, the disclosure of each of which hereby is incorporated by reference in entirety. However, certain amorphous resins may be difficult to process without the use of a solvent because some resins do not have a sharp melting point and exhibit substantial viscosities, which may work against the formation of emulsions. In addition, certain amorphous resins are more susceptible to molecular weight degradation in the solvent-free process.
Solvents may be added to amorphous resins to reduce the viscosity and to permit necessary reorientation of chain end, which may stabilize and form particles which lead to the formation of stable latexes.
Previous single-solvent and two-solvent processes are known to produce latex particles of sizes of 140 to 230 nm (see, e.g., U.S. Pub. Nos. 20110200930 and 20110281215, the disclosure of each of which hereby is incorporated by reference in entirety), which may not be suitable for effective dispersion of toners comprising high solid loading of, for example, carbon black pigment particles. It would be advantageous to provide a solvent-based process for the preparation of latex resins, particularly latex resins formed from low molecular weight and high molecular weight amorphous resins that have a particle size of 100 nm or less.